It is well known to use elastic bands (also known as elastic straps) made of rubber or other elastomer compounds to provide a tensile biasing force between machine elements. For example, U.S. Pat. Nos. D280,224 to Wilson and D315,936 to Wilson et al. disclose straps for use on exercise machines, and U.S. Pat. No. D361,261 to Amburgey et al. discloses a suspension band resembling those used on toy riding apparatus.
A common configuration for elastic bands comprises an elastic center section extending between two elastic retaining sections, each retaining section having an attachment hole formed therethrough for connection to one of the machine elements which is to be biased. Such bands are commonly manufactured from molded rubber compounds or other elastomeric materials which are cured under elevated heat and pressure. Bands having different tensile bias values and/or different elongation values can be obtained by changing the cross-sectional area of the center section and/or by changing the rubber compound or elastomer compound used in the center section.
When an elastic band of the type described above is placed in operational tension (i.e., tension directed along a line connecting the attachment holes), portions of the retaining sections tend to elongate in the direction of the applied tension. If the retaining section elongates, portions of the inboard edge of the retaining section are pulled away from the machine element to which it is attached, thereby increasing the span of the attachment hole in the direction of the applied tension and creating a gap between the band and the machine element. Any object which is placed into this gap when the band is elongated by tension can be pinched or crushed between the band and the machine element when the tension is released and the band returns to its original configuration. It is therefore frequently desirable to reinforce the retaining section of elastic bands in order to reduce the amount of attachment hole elongation which occurs for a given tension and thereby minimize or eliminate any gap and the associated pinching or crushing hazard.
Toy riding apparatus of the type having a rider support device (commonly shaped to resemble a horse) which is elastically suspended from a base or frame such that the child can rock back and forth to simulate riding are well known. Many such rocking toys use coil springs connected between the rider support (e.g., the horse) and the base for their suspension mechanism. Some such riding toys, however, use elastic bands of the type described above rather than coil springs for their suspension mechanism. U.S. Pat. No. 5,328,410 to Amburgey et al. discloses such a toy riding apparatus using elastic bands for suspending the rider support device from a base. Avoidance of any gaps between the elastic bands and the support frame caused by elongation of the bands' retaining sections is especially important in the case of toy riding apparatus because children may not appreciate the hazards and can be injured if their fingers, toes, etc. should become caught in such gaps when the tension is released.
Elastic bands known in the prior art utilize several approaches to reinforce the retaining section and reduce attachment hole elongation. Some elastic bands include retaining sections having outboard walls (i.e., the walls on the outboard half of each retaining section) which are thick compared to the span of the attachment hole. For purposes of this application, a wall is considered thick if the wall has a thickness, measured radially from the center of the attachment hole, which is at least equal to the span of the respective attachment hole (the span being the diameter of a round hole or the distance across a non-round hole measured perpendicular to the line of tension). In comparison to bands having thin (i.e., not thick) walls, such radially thick outboard walls can reduce the amount of retaining section elongation and the size of the attachment hole gap for a given tension in the band. However, significantly more material is required to produce bands having thick walls, and the radial protrusion of the walls can present a problem in situations where space is limited, or in situations where the protruding walls are aesthetically undesirable.
Other elastic bands are known in which two or more different elastomer compounds are cured together in adjacent portions of a single mold to form a unitary article which, after curing, still has identifiably different compounds in different areas of the band. Such bands are sometimes known as multi-compound bands. A multi-compound band can be formed with a relatively hard (i.e., higher durometer) rubber compound in the retaining sections and a relatively soft (i.e., lower durometer) rubber compound in the central section. In such bands, the hard rubber compound reinforces the retaining section and reduces elongation of the attachment hole in comparison to a band formed completely of the soft rubber, while the soft rubber in the central section provides a lower tensile biasing force in comparison to a band formed completely of the hard rubber. Such multi-compound bands can thus reduce retaining section elongation and the size of the associated gap without requiring thick-walled retaining sections. However, the manufacture of multi-compound bands is more complex than single compound bands since the different uncured rubber compounds must be accurately placed in their respective areas of the mold cavity and prevented from shifting as the rubber is cured. Accordingly, multi-compound bands can be more expensive to produce than single compound bands. In addition, as a multi-compound band ages under tension and is cycled in use, the different rubber compounds can sometimes separate or "de-bond" from one another along the surface of the band. Even though the band's overall elastic properties may change little when such surface separation occurs, it is nonetheless typically viewed as a failure of the band.
It is also known to embed a smooth-walled metallic cylinder within the rubber matrix of the retaining section of a multi-compound elastic band to further reinforce the retaining section against elongation under tension. However, the manufacture of bands with embedded smooth-walled metallic cylinders typically requires the cylinders to be carefully cleaned (e.g., using sandblasting, solvents, etchants, or the like) to remove any surface dirt, oil or rust, and then coated with a chemical bonding agent to ensure that a good bond is formed between the metallic cylinder walls and the surrounding elastomer compounds in the retaining section during curing. Without a good bond, the rubber on the inboard half of the retaining section can be pulled away from the metallic cylinder when tension is applied to the band, thereby forming an internal void within the retaining section which can lead to band failure. Further, the cylinders used in such bands must have a precise length to avoid manufacturing problems. If the cylinder is too long, the cylinder can prevent the mold from closing properly; if the cylinder is too short, the cylinder can move around in the mold during the molding process. In addition, the manufacture of multi-compound bands with embedded smooth-walled metallic cylinders is further complicated because the solid cylinders can block the flow of uncured rubber into certain portions of the mold. Also, as with all multi-compound bands, the various different uncured rubber compounds must be accurately placed in their respective areas of the mold cavity and prevented from shifting as the rubber is cured.
A need therefore exists, for an elastic band formed from a single rubber or elastomer compound, which is reinforced to resist elongation of the retaining section under tension, and which does not require surface preparation or precise lengths for its embedded metallic components.
A need further exists, for a toy riding apparatus which incorporates elastic bands for suspension of the rider support device, wherein the bands are formed from a single rubber or elastomer compound, are reinforced to resist elongation of the retaining section under tension, and do not require surface preparation or precise lengths for its embedded metallic components.